soil-P Availability Research Articles

The Effect of N, P, K and Si Fertilizers on Some Soil Chemical Properties, N, P uptake and Growth of Black Rice (Oryza sativa L. indica) in Ultisols

This study aims to determine the effect of the combination of fertilizers N, P, K, and Si on the pH, N-total, Al-dd, N, P- uptake, and grown of black rice (Oryza sativa L. indica) in Ultisols from Jasinga. This research was conducted from October 2021 to January 2022 at the Experimental Land for Soil Chemistry and Plant Nutrition in Jatinangor, Faculty of Agriculture, Universitas Padjadjaran, Jatinangor, Sumedang, West Java with an altitude of 752 meters above sea level. The experimental design was carried out using a Randomized Block Design (RAK) consisting of eight treatments and three replications, consisting of: control; 1 N, P, K without Silica; 1 N, P, K + ½ Silica; 1 N, P, K + 1 Silica; 1 N, P, K + 2 Silica; ¾ N, P, K + 1 Silica; ¾ N, P, K + 1½ Silica; ¾ N, P, K + 2 Silica; and without N, P, K + 2 Silica. The results showed that the combination of fertilizer doses of 1 N, P, K (Urea 300 kg/ha, SP-36 100 kg/ha, and KCl 100 kg/ha) with 1 Silica (2 mL/L) gave the best black rice yields in increasing plant height by 60.34 cm and number of tillers 34, plus those dose is the best dose in increasing soil pH by 5.63, but the fertilizer dose was not able to increase soil P-Availability and N-Total.

Soybean (Glycine max) rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorus-mineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus (P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean (Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase (AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the α-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoC-harboring bacteria, such as Cupriavidus.

Lipid profiles of plants and soil microbial communities are shaped by soil parent material in Australian sclerophyll forests

Background and aimsPlant and soil microbes can reduce their phosphorus (P)-requirements by replacing phospholipids with non-P containing lipids (e.g., galactolipids, sulfolipids, and betaine lipids). There have been few studies of this process in the field (i.e., in natural ecosystems); thus, it is unclear whether a similar replacement of phospholipids with non-P lipids occurs across natural gradients of soil P-availability.MethodsWe compared the membrane lipid profiles of plant leaves, roots, and soil microbial communities between two adjacent native Australian sclerophyll forest ecosystems—one situated on a severely P-deficient sandstone-derived soil and the other on a comparatively P-rich shale-derived soil. The herbaceous species, Lomandra longifolia, which occurred across both soils was sampled, along with two Myrtaceae tree species associated with each soil type.ResultsThe phospholipid content of plant leaves and soil microbes was two- to three-fold greater in the shale site than the sandstone site, but non-P lipid content did not differ between sites.ConclusionOur results indicate that plants and soil microbes can have a lower investment of P into phospholipids in response to P-deficiency without a concomitant increase in non-P lipid content. Modulations in phospholipid concentration occurred across all plant- and soil microbial-associated phospholipid classes.

Direct foliar acquisition of desert dust phosphorus fertilizes forest trees despite reducing photosynthesis.

Phosphorus (P) availability to forest trees is often limited by local soil conditions that increase its fixation to soil minerals. In certain regions, atmospheric-P inputs can compensate for low soil-P availability. Among atmospheric-P sources, desert dust is the most dominant. However, the effects of desert dust on P nutrition and its uptake mechanisms by forest trees are currently unknown. We hypothesized that forest trees that naturally grow on P-poor soils or soils with high soil-P fixation capacity can acquire P from desert dust deposited on their leaves via direct foliar uptake, bypassing the soil, thus promoting tree growth and productivity. We performed a controlled greenhouse experiment with three forest tree species: Palestine Oak (Quercus calliprinos) and Carob (Ceratonia siliqua), native to the NE edge of the Saharan desert, and Brazilian peppertree (Schinus terebinthifolius), native to the Atlantic Forest in Brazil, which is located on the western part of the trans-Atlantic Saharan dust route. To simulate natural dust deposition events, the trees had desert dust applied directly upon their foliage and were monitored for growth and final biomass, P levels, leaf surface pH and the rate of photosynthesis. The dust treatment increased the P concentration significantly by 33-37% in Ceratonia and Schinus trees. On the other hand, trees that received the dust displayed a 17-58% reduction in biomass, probably related to particle coverage of the leaf surface that inhibited photosynthesis by 17-30%. Overall, our findings show that direct P uptake from desert dust can be an alternative P uptake pathway for multiple tree species under P-deficient conditions, with implications for forest trees' P economy.

Growth and tissue nutrient responses of adults of Sarracenia alata to prey exclusion, nutrient addition, and neighbor reduction.

Carnivorous plants are often associated with nutrient-poor soils and fires. Fire can decrease available soil nitrogen (N) and increase light availability, thus potentially favoring carnivory if prey provide N. Prey can also be a source of phosphorus (P), however, and soil P-availability often increases and competition for prey can decrease following fire. Carnivory thus might be more advantageous before fire when prey and/or soil P are more limiting. We examined nutrient limitation of growth in a carnivorous plant, Sarracenia alata, in a wet pine savanna in southeastern Mississippi, USA. We measured growth and N:P tissue concentration responses of adult plants to a factorial arrangement of prey capture, neighbor reduction, and addition of N, P, and ash to the soil. We tested two hypotheses: (1) Prey provide N, and neighbor reduction and ash addition increase light and soil P and thus the benefit of carnivory; and (2) Prey provide P, neighbor reduction increases prey and/or P, and prey exclusion reduces growth the most when neighbors are not reduced. The exclusion of prey reduced growth more when neighbors were not reduced, an effect that was ameliorated slightly by the addition of P to the soil (the P-limitation hypothesis). Prey exclusion caused a decrease in tissue P when N was added to the soil. The results of this study with adult plants differed from those of a previous study using small juvenile plants, suggesting a shift from light limitation to P and prey limitation with increasing size.

Application of Biocom-Phosphate Solubilizing Fungi and Coal Fly-Ash to Increase P-Availability of Peat Soil in Kalimantan

The peatlands have the potential to support food security efforts. However, there is have constraints on soil fertility, especially the P nutrients availability. The biotechnology approach, the application of ameliorant (biochar-compost carrier medium (biocom)) enriched with phosphate solubilizing fungi (PSF) and coal fly ash (CFA), was expected to increase the P-availability in peat soils. The research aimed to study the application of biocom enriched with PSF and CFA to increase soil P-availability and plant P-uptake. The study was conducted using peat soil media with the formulation of CFA and biocom enriched with PSF and CFA as treatments. The treatment effect was observed through soil P available and plant P uptake of maize. The results showed PSF application was inconsistent in improving P available in peat soils in Kalimantan. In Central Kalimantan, Biocom + PSF was able to increase P available in peat soils by up to 406.18% (A. oryzae-Tb7) and 353.44% (N. fischeri-Tm8). However, in South Kalimantan P available in peat soil was only 8.04% (A. oryzae-Tb7) and 12.86% (N. fischeri-Tm8). The CFA+ (biocom+PSF) formulation increased P available in Central Kalimantan peat soils, but it was different from South Kalimantan peat soils. The application of biocom+PSF and CFA has not been able to increase the P uptake of maize plant in peatlands of South Kalimantan.

Using Soil P Tests and P-Sorption Index to Predict P Requirement for Cassava Grown in Tropical Upland Sandy Soils

ABSTRACT The phosphorus (P) sorption index and efficiency of P extracting methods were investigated to quantify the available P content for accurate recommendations regarding cassava P fertilizer application in the sandy soils of Thailand. Phosphorus sorption isotherms were examined to predict the response of soils to the P fertilizers applied. Six rates of P fertilizers (0, 12.5, 25, 37.5, 50 and 62.5 kg P2O5 ha−1) were applied in a randomized complete block design at five field sites in major cassava-growing areas. The efficiency among the Bray II, CaCl2 and Mehlich III extracts was also tested by comparing their capacity to predict crop response. The P adsorption capacities of all soils were in the range 39.4–106 mg kg−1; therefore, there were classified as low P-sorbed soils. Phosphorus fertilizer produced significantly higher aboveground biomass than did zero-P fertilization. The critical P level adequate for 95% of the maximum yield was in the range 0.14–0.26 mg P L−1. The equation for calculating P fertilizer using soil P extracted based on the Bray II, CaCl2 and Mehlich III methods had accuracy levels of 73, 65 and 72%, respectively. Bray II was slightly superior to Mehlich III for use in soil-P availability indices, both of which were recommended for P fertilizer assessment.

Influence of Biological Agents in Controlling Nematodes and Improving Growth of Coffee Seedling and Soil P-Availability

Pests and diseases cause significant yield losses in coffee cultivation in Indonesia. In particular, Pratylenchus coffeae is the most common nematode in Indonesia known to harm coffee plants. In dealing with the threat of P. coffeae, mycorrhiza is used as a biological agent to increase the growth of coffee plants as well as control the nematode. This experiment was conducted to determine the formulation of biological agents in the form of mycorrhizae enriched with mycorrhizal helper bacteria (MHB) to control nematodes and increase the growth of coffee seedlings and soil P-availability. The mycorrhizae used in this experiment were Glomus spp., while the liquid MHB formula used Pseudomonas diminuta and Bacillus subtilis. The randomized block design was used with treatments consisting of control (without biological agents); inoculation of P. coffeae; Glomus + P coffeae; Glomus + MHB 108+ P coffeae; Glomus + MHB 109+ P coffeae. Observations were made on the growth of coffee seedlings and the nematode population of P. coffeae 10 weeks after administered treatments. Results revealed that inoculation of biological agents Glomus spp. + the liquid MHB formula increased the growth of coffee seedlings, soil P-availability, and reduced the population of P. coffeae. The best treatment was Glomus spp. + MHB 108 which can reduce the population of P. coffeae by 65%.

Effects of Faba Bean Strip Cropping in an Outdoor Organic Tomato System on Soil Nutrient Availability, Production, and N Budget under Different Fertilizations

Crop diversification has been identified as a tool to improve both productive and environmental performances of organic horticulture. We tested the introduction of faba beans in a tomato cropping system—both as preceding crop and in strip cropping (SC)—under different fertilization strategies—faba residues, animal manure, and vegetable compost. We studied: (i) the tomato nutrient uptake and yield and quality; (ii) the soil-N and P, the N-budget, and the mycorrhizal colonization. SC did not provide consistent positive effects on tomato production and quality, namely the N-uptake, N in the tomato yield, the mean fruit weight, and the sugar accumulation in berries, regardless of the type of fertilizers applied. SC improved the tomato dry yield and P-uptake, especially in years when the faba growth and the subsequent yield were problematic. Faba residues could provide sufficient N to sustain tomato production but care should be given in balancing additional N-inputs. Organic fertilization increased the soil-N concentration but did not always translate into an increased yield and a higher quality production, with the risk of escalating N-losses. SC improved the soil-P availability and mycorrhizal colonization in tomato, due to the rhizobia–mycorrhiza-mycorrhiza association, especially when coupled with organic fertilization. Finally, introducing faba as SC holds potential to improve the productive and environmental performance of organic tomato production.

Effect of Land Use Change on Soil Physico-chemical Characteristics in Sungai Batang, east part of Maninjau caldera

Land-use change from the forest to others will affect the soil’s physicochemical properties. The research was conducted to identify soil physicochemical properties affected by land-use change in Sungai Batang, the east-south part of Maninjau caldera. The research used a survey method from which soil was sampled at four different types of land use (forest, bushland, mixed garden, and paddy soil) at 0-30 cm depth with three replicates. The results show that the soil in Sungai Batang was still developing. It was indicated by coarse soil texture (clay loam to sandy clay loam). Land-use change from the forest to other uses has altered some soil physicochemical properties. It increased soil bulk density and decreased total soil porosity, permeability rate, SOM content, and total-N. However, there was an increase in soil characteristics, especially soil P-availability, CEC, Ca- and Na-exchangeable . While the soil pH (H2O), K-and Mg-exchangeable stayed the same. In general, land use changed from forest to other use, mostly farming land degraded physicochemical characteristics of the soil derived from volcanic materials in Sungai Batang. That was mainly due to the decrease in SOM content.

PENGARUH ECOENZYM DAN SP-36 TERHADAP BEBERAPA SIFAT KIMIA TANAH DAN PERTUMBUHAN TANAMAN SAWI (Brassica juncea L.) PADA ULTISOL

This experiment was conducted in a Greenhouse of Soil Science Department from March to May 2021. Soil properties analysis was carried out at the Laboratory of Chemistry, Biology and Soil Fertility of Soil Science Department, Faculty of Agriculture, Sriwijaya University. This experiment aims to study the effect of ecoenzym and SP-36 application on pH and P availability and growth of Mustard planted on Ultisol. This experiment was designed using the Completely Randomized Design consisting of 8 treatments which were B0: Control, B1: 10 ml L-1 ecoenzyme (EE), B2: 5 ton ha-1 of EE solid waste, B3: 50% recommended dose of 56.25 kg SP-36 ha-1, B4: 100% recommended dose of 112.5 kg SP-36 ha-1, B5: 10 ml L-1 EE + 5 ton ha-1 EE solid waste, B6: 50% recommended dose of 56.25 kg SP-36 ha-1 + 10 ml L-1 EE + 5 ton ha-1 EE solid waste, B7: 100% recommended dose of 112.5 kg SP-36 ha-1 + 10 ml L-1 EE + 5 ton ha-1 of EE solid waste. The treatment was replicated 3 times thus the total of experiment were 24 units. Variables observed were soil pH and P availability, growth and yield of Mustard. The results showed that the treatments of ecoenzyme and ecoenzyme solid waste and SP-36 fertilizer had significant effects on the soil pH, P-Availability, plant height, leaves number, root length, wet and dry weight of mustard. The B4 treatment with SP-36 treatment dose of 112.5 kg ha-1 resulted the best effect on soil pH and soil P-Availability, growth and yield of mustard

Changes in Soil-Phosphorus Fractions by Nitrogen and Phosphorus Fertilization in Korean Pine Plantation and Its Natural Forest

Phosphorus (P) is the restraining aspect in the forest ecosystem, particularly in temperate regions, and makes the ecosystem more liable to nitrogen (N)-derived acidification. However, it remains poorly understood how N and P fertilization together affects soil-P availability and other soil properties. To address this question, a factorial experiment was conducted with N and P additions under two forest ecosystems, i.e., Korean pine plantation (KPP) and natural Korean pine forest (NKPF). Both forests were divided in to three subplots and each subplot underwent four different treatments, i.e., C: control (no N and P addition), L: Low treatment (5 g N m−2 a−1 + 5 g P m−2 a−1), M: Medium treatment (15 g N m−2 a−1 + 10 g P m−2 a−1), and H: High treatment (30 g N m−2 a−1 + 20 g P m−2 a−1). Results revealed that the soil-P fractions changed during N and P fertilization over time although organic-P (Po) fractions were lower than inorganic-P (Pi) fractions. The residual P was increased overall, along with N deposition in soil. Soil organic carbon (SOC) was more present in NKPF soils as compared to KPP. Principal component analysis (PCA) indicated that at medium treatment there is maximum availability of P fractions as compared to other treatments in both forests, while high treatment showed some fixation of P in soils across both forests. Furthermore, SOC showed a negative correlation with residual P, while pH showed a positive correlation. Total N in soil showed a negative correlation with soil pH and residual P. Therefore, it is recommended that application of N and P at the rate of 15 g N m−2 a−1 + 10 g P m−2 a−1 is suitable in these two forest types to enhance P availability.

Global patterns and drivers of soil total phosphorus concentration

Abstract. Soil represents the largest phosphorus (P) stock in terrestrial ecosystems. Determining the amount of soil P is a critical first step in identifying sites where ecosystem functioning is potentially limited by soil P availability. However, global patterns and predictors of soil total P concentration remain poorly understood. To address this knowledge gap, we constructed a database of total P concentration of 5275 globally distributed (semi-)natural soils from 761 published studies. We quantified the relative importance of 13 soil-forming variables in predicting soil total P concentration and then made further predictions at the global scale using a random forest approach. Soil total P concentration varied significantly among parent material types, soil orders, biomes, and continents and ranged widely from 1.4 to 9630.0 (median 430.0 and mean 570.0) mg kg−1 across the globe. About two-thirds (65 %) of the global variation was accounted for by the 13 variables that we selected, among which soil organic carbon concentration, parent material, mean annual temperature, and soil sand content were the most important ones. While predicted soil total P concentrations increased significantly with latitude, they varied largely among regions with similar latitudes due to regional differences in parent material, topography, and/or climate conditions. Soil P stocks (excluding Antarctica) were estimated to be 26.8 ± 3.1 (mean ± standard deviation) Pg and 62.2 ± 8.9 Pg (1 Pg = 1 × 1015 g) in the topsoil (0–30 cm) and subsoil (30–100 cm), respectively. Our global map of soil total P concentration as well as the underlying drivers of soil total P concentration can be used to constraint Earth system models that represent the P cycle and to inform quantification of global soil P availability. Raw datasets and global maps generated in this study are available at https://doi.org/10.6084/m9.figshare.14583375 (He et al., 2021).

Allocation of foliar-P fractions of Alhagi sparsifolia and its relationship with soil-P fractions and soil properties in a hyperarid desert ecosystem

Desert vegetation in the juncture of the Qira oasis and the Taklamakan Desert typically grows on phosphorus (P)-poor soils. Alhagi sparsifolia Shap. (A. sparsifolia), as widely distributed natural vegetation in this area, not only has crucial ecological effects of wind sheltering and sand fixation, but also is an excellent forage resource. Researchers are increasingly interested in the foliar-P utilization strategy of A. sparsifolia that allows it to survive in extremely P-impoverished soils. Therefore, A. sparsifolia growing in four different soil sites with differing availability of P in this area were studied, and leaves and 0–100 cm soils were collected. Foliar total nitrogen (N), total-P and P fractions (metabolic-P, nucleic acid-P, structural-P, and residual-P) were determined. Soil labile-P (resin-P, NaHCO3-Pi, and NaHCO3-Po), moderately labile-P (NaOH-Po and NaOH-Pi), stable-P (HCl-P and residual-P), and basic soil properties were determined. Our findings showed that A. sparsifolia growth was highly likely to be limited by soil-P in this area, and the concentrations of foliar total-P and young leaf metabolic-P increased with increasing soil-P availability, while foliar-N was relatively constant. Comparatively, A. sparsifolia allocated a higher proportion of foliar-P to nucleic acid-P and a lower proportion to structural-P, as soil-P availability decreased. Moreover, foliar metabolic-P, nucleic acid-P, and structural-P had the strongest positive response to soil labile-P in topsoil. Furthermore, soil electrical conductivity (EC), labile-P, and moderately labile-P influenced foliar-P fractions. Comprehensively, variation in foliar-P allocation patterns of A. sparsifolia varied across the four soils with differing available-P and were closely related to soil-P fractions and properties. These results will help us better understand A. sparsifolia foliar-P utilization strategy and their potential responses to environmental nutrients.

Adjusting P-K Fertilization and Liming Strategies to Enhance Yield of Cherry Tomato Plants Grown on an Oxisol

ABSTRACT Although cherry-tomato is becoming more popular in the last years, there are no specific recommendations for P and K fertilization or liming strategies for this specific variety. Our aim was to assess rates of P and K and liming strategies in order to improve the yield of cherry-tomato grown on an Oxisol with a limited P-availability. Two pot experiments were developed. In the first-one, a two-factor factorial design was developed with 4 P (first-factor) and 4 K rates (second-factor), being these rates the 0%, 50%, 100%, and 200% of the recommended fertilization for tomato in South-Brazil. In the second experiment, the soil pH (4.3) was adjusted to 5.5, 6.0, and 6.5 with limestone. Soil P-availability, plant growth, diameter, number of fruits and cherry tomato yields were increased with the P addition, while a non-significant effect was observed after adding K. The highest yield was produced with 50% of the suggested amount of P for tomato in comparison with the non-fertilized plants (yield increase of 674%), while higher P rates (100% and 200%) produced a lower yield increase. The significant effect of soil liming was observed on increase of the flower bunches number when the soil pH was amended to 6.5. Cherry-tomato requirements seem to be different from the recommended for other varieties. Our results indicate that higher yields were achieved with a lower amount of chemical inputs than the recommended for tomato in general, stressing the importance of P for tomato cherry production over the other factors assessed here.

Eucalypts and low phosphorus availability: between responsiveness and efficiency

Twenty-four species of eucalypts were studied regarding their ability to grow under low P and their responsiveness to P inputs. Growth and photosynthesis-related parameters were evaluated. Growth of all species was influenced by low P availability. No significant correlation was found between leaf P concentration and biomass, indicating that P concentrations in leaves cannot be solely considered an indication of the responsiveness to P in eucalypts. Species responsive to P-input (high agronomic P efficiency values, APE) were those with low P use efficiency - PUE (here assessed as relative efficiency of P-use, REP) and low P uptake efficiency (PUpE). But, non-responsive species were related to higher P-efficiency under low soil P-availability. Eucalyptus tereticornis, E. cladocalyx, E. globulus and E. camaldulensis were efficient under low-P availability. Whereas, E. crebra and E acmenoides were the most responsive species, with high APE, suggesting that for these species P-inputs are needed to guarantee plant growth. The root:shoot ratio remained constant at different P availabilities, suggesting that biomass allocation towards the root in response to P and greater investment in roots were not correlated with greater PUE. Under limited P, E. robusta and E. botryoides exhibited low foliar P contents and higher root:shoot ratios than those of other species with higher P contents, indicating that greater root investment does not necessarily result in greater PUE. The results suggest that the divergence among species is probably related to different mechanisms, which may improve P-use efficiency.

Seasonal Alterations in Organic Phosphorus Metabolism Drive the Phosphorus Economy of Annual Growth in F. sylvatica Trees on P-Impoverished Soil.

Phosphorus (P) is one of the most important macronutrients limiting plant growth and development, particularly in forest ecosystems such as temperate beech (Fagus sylvatica) forests in Central Europe. Efficient tree internal P cycling during annual growth is an important strategy of beech trees to adapt to low soil-P. Organic P (Porg) is thought to play a decisive role in P cycling, but the significance of individual compounds and processes has not been elucidated. To identify processes and metabolites involved in P cycling of beech trees, polar-metabolome and lipidome profiling was performed during annual growth with twig tissues from a sufficient (Conventwald, Con) and a low-soil-P (Tuttlingen, Tut) forest. Autumnal phospholipid degradation in leaves and P export from senescent leaves, accumulation of phospholipids and glucosamine-6-phosphate (GlcN6P) in the bark, storage of N-acetyl-D-glucosamine-6-phosphate (GlcNAc6P) in the wood, and establishing of a phospholipid “start-up capital” in buds constitute main processes involved in P cycling that were enhanced in beech trees on low-P soil of the Tut forest. In spring, mobilization of P from storage pools in the bark contributed to an effective P cycling. Due to the higher phospholipid “start-up capital” in buds of Tut beeches, the P metabolite profile in developing leaves in spring was similar in beech trees of both forests. During summer, leaves of Tut beeches meet their phosphate (Pi) needs by replacing phospholipids by galacto- and sulfolipids. Thus, several processes contribute to adequate Pi supply on P impoverished soil thereby mediating similar growth of beech at low and sufficient soil-P availability.

Incorporation of fallow weed increases phosphorus availability in a farmer’s organic rice fields on allophanic Andosol in eastern Japan

ABSTRACTWe investigated the amount of soil phosphorus (P) in a farmer’s paddy fields under organic farming (OF) for various periods from 0 to 22 years as well as other farmers’ fields under conventional farming. All the fields are located in allophanic Andosol with long history of P fertilizer application, and some of them have been converted to OF across years. After conversion to OF, P was supplied only with winter fallow weeds mainly Foxtail (Alopecurus aequalis), rice residues (rice bran and straw), and guano. We determined total-P (Tot-P) and plant-available P (Av-P), which consists of Truog-P (Tru-P) and Bray-2-P under reducing condition with ascorbic acid (Asc-P), in soils of each field. For both Av-Ps, the ratio to Tot-P increased across years under OF following quadratic functions with both linear and quadratic terms being statistically significant. The ratios showed little changes for the initial 15 (Tru-P) or 10 (Asc-P) years and increased rapidly thereafter. These temporal changes in Av-P were consistent with the rapid increase of the amount of P accumulated in the winter fallow weeds and incorporated in the fields after beginning of OF. These results led us to the hypothesis that the incorporation of winter weeds has contributed to the increase of Av-P in the organic fields across years. We tested this hypothesis by investigating temporal changes of Av-P after suspending the weed incorporation for 2 consecutive years in plots of the organic fields. Both Av-Ps were significantly greater in plots with continued weed incorporation (CWI) than those in plots with its suspension. We further found that the increase of Asc-P in plots with CWI was 4.9-fold the input of total P in the incorporated weeds. This suggests that the incorporation of winter fallow weeds enhanced soil-P availability beyond the supply of P accumulated in the weeds.

Phosphorus nutrition of Populus × canescens reflects adaptation to high P-availability in the soil.

Phosphorus (P) constitutes one of five macronutrients essential for plant growth and development due to the central function of phosphate in energy metabolism, inheritance and metabolic control. In many ecosystems, plant available soil-P gets limited by soil aging. Hence, plants have developed adaptation strategies to cope with such limitation by an efficient plant and ecosystem internal P-cycling during annual growth. The natural floodplain habitat of fast-growing Populus × canescens is characterized by high soil-P availability. It was thus expected that the P-nutrition of P. × canescens had adapted to this conditions. Therefore, different P-fractions in different twig tissues were investigated during two annual growth cycles. The P-nutrition of P. × canescens markedly differs from that of European beech grown at low soil-P availability (Netzer F, Schmid C, Herschbach C, Rennenberg H (2017) Phosphorus-nutrition of European beech (Fagus sylvatica L.) during annual growth depends on tree age and P-availability in the soil. Environ Exp Bot 137:194-207). This was mainly due to a lack of tree internal P-cycling during annual growth indicated by the absence of P-storage and remobilization in twig bark and wood. Hence, strategies to economize P-nutrition and to prevent P-losses had not developed. This fits with the fast-growth strategy of P. × canescens at unrestricted P-availability. Hence, the P-nutrition strategy of P. × canescens can be seen as an evolutionary adaptation to its natural growth habitat.

Phosphorus-nutrition of European beech (Fagus sylvatica L.) during annual growth depends on tree age and P-availability in the soil

Forest ecosystems have often developed on phosphorus (P) −limited soils and, thus, are thought to require an efficient P-nutrition strategy during annual growth to sustain sufficient P-supply for growth and development. The present study was aimed at characterizing seasonal changes in P-composition and concentrations in different organs and transport tissues of mature and young European beech (Fagus sylvatica L.) trees growing at different soil-P availability. From these changes, a model of tree internal P-cycling strategy as dependent on tree age and P-availability was developed. For this purpose, leaves, stem tissues and roots, as well as xylem sap and phloem exudate were collected from adult trees and their progeny at two field sites in southern Germany, one with low but sufficient (Conventwald field site), and one with extremely low (Tuttlingen field site) P-availability in the soil. P-cycling during annual growth with bark and wood as the main P-storage tissues in winter is strongly indicated and was much more pronounced in adult beeches compared to its progeny, and of higher significance at extremely low soil-P. The re-use of stored organic phosphorus containing compounds (Porg) from bark and wood during spring and the resorption of Porg from senescing leaves can be seen as a strategy to enhance tree internal P-cycling efficiency, especially in adult trees growing at extremely low P-availability. The consequences of tree internal P-cycling for ecosystem P-losses and its dependency on tree age and soil P-availability are discussed.